British police said the incident, in which at least 50 people were injured, was being treated as a terrorist incident. Police carried out a controlled explosion on a suspect device several hours after the blast.

Police set up a cordon outside the Manchester Arena in northern England where US singer Ariana Grande had been performing in Manchester, Britain, May 22.
(Reuters Photo)

A witness who attended the concert said she felt a huge blast as she was leaving the arena, followed by screaming and a rush by thousands of people trying to escape the building. A video posted on Twitter showed fans, many of them young, running from the venue.

Concert goers react after fleeing the Manchester Arena in northern England where US singer Ariana Grande had been performing in Manchester, Britain, May 22.
(Reuters Photo)

“We were making our way out and when we were right by the door there was a massive explosion and everybody was screaming,” concert-goer Catherine Macfarlane told Reuters.

“It was a huge explosion - you could feel it in your chest. It was chaotic. Everybody was running and screaming and just trying to get out.”

Armed police stand guard at Manchester Arena after reports of an explosion at the venue during an Ariana Grande gig in Manchester on May 22.
(AP)

A spokesman for Ariana Grande, 23, said the singer was “okay”.

Manchester Arena, the largest indoor arena in Europe, opened in 1995 and is a popular concert and sporting venue.

Emergency services work at Manchester Arena after reports of an explosion at the venue during an Ariana Grande gig in Manchester, England, May 22.
(AP Photo)

Britain is on its second-highest alert level of “severe” meaning an attack by militants is considered highly likely.

Two women wrapped in thermal blankets look on near the Manchester Arena, where US singer Ariana Grande had been performing, in Manchester, Britain.
(Reuters )

British counter-terrorism police have said they are making on average an arrest every day in connection with suspected terrorism.

Emergency services work at Manchester Arena after reports of an explosion at the venue during an Ariana Grande gig in Manchester, England, on Monday.
(AP Photo)

In March, a British-born convert to Islam ploughed a car into pedestrians on London’s Westminster Bridge, killing four people, before stabbing to death a police officer who was on the grounds of parliament. He was shot dead at the scene.